Field of the Invention
The present invention relates to computer networks. More specifically, the present invention relates to a method and an apparatus accelerating the expiration of local resource records in a local cache.
Related Art
The explosive growth of broadband technology and network infrastructure, coupled with continually decreasing prices, has led to an increasing number of computer networks in homes and small businesses. Along with this small-office/home-office network revolution comes the daunting task of configuring and administering these networks. Plug-and-play network protocols, such as Apple Computer Inc.'s Rendezvous, have been developed to simplify administration tasks. Within Rendezvous, devices, such as printers, scanners, and network attached storage, automatically configure themselves and advertise their services upon being connected to the network. Computer systems on the network add resource records for these devices to their local cache upon receiving the advertisement, thus maintaining a list of available services on the network.
Along with the benefits of maintaining a local cache come problems. Computer systems on the network must continually update their cache records to maintain an accurate list of available services. Traditionally, computer systems have done this by querying the services and waiting for a response. If a response is not received within a specified amount of time, or after a specified amount of tries, the record pertaining to the service or associated device is deleted from the cache. Frequently polling services (and related devices) in this way provides a more accurate list of services, but can dramatically increase network traffic.
One problem with caching resource records arises from stale data. A device may be removed from the network in a manner that does not allow it to report the unavailability of its services. Power failures, improper shutdowns, and disconnected network cables are just a few examples of common occurrences that can cause invalid cache records. Often, users unsuccessfully try to use a service because a corresponding locally cached record for the service is invalid, which causes the service incorrectly to show up locally as being available. This can result in frustration to the user because the service still shows up as available in the local list. Moreover, even if some cache records are invalidated on some computer systems, the same invalid cache records may still be present on other computer systems on the network.
Hence, what is needed is a method and an apparatus for maintaining resource records in a cache without the limitations listed above.